Induction-furnace.



c. P. STBINMETZ. INDUCTION FUBNAGB. APPLUATIOI FILED JULY 26, 1911.

Patented Oct. 29,1912.

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CHARLES P. STEINMETZ, OF SCHENECTADY, NEW YORK, ABSIGNOB;

ELECTRIC COMPANY, A CORPORATION OF. NEW YORK. i,

I NDUCTION -FUBNACE Specification of Letters Patent.

Patented oet. 29,v 1912.

` Application led J'uly 26, 1911. NSerial No. 640,627.

To allwhom it may concern; i

Be it known that I, CHARLES P. S'rnrN- METZ, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Induction- Furnaces, of which the following is a specification.

My invention relates to electric induction furnacesand comprises` a furnace 1n which the primary and secondary windings are in close inductive relation and which, therefore, operates with a high power factor.

MetallurgicalA induction furnaces as formerly constructed had a considerable amount of -leakage flux,'in other words a portion of .the primary flux completed its magnetic circuitwithout threading the secondary, resulting in a low power factor. As the magnetic leakage was due largely to the necessity of loc-ating the primary far enough away from the heated secondary to secure suliicient cooling, the power factor was lowered as the size of the furnace was increased.

In accordance with my invention the primary and secondary are brought into the closest inductive relation possible by constituting the furnace crucible itself the primary winding. For this purpose, it consists of metal, the charge beinginsulated therefrom by a suitable lining. The crucible primary is supplied with a current of sufficiently high amperage. and low voltage by making it an integral part of the secondary of a step-down transformer which thus constitutes part of the furnace.l

The accompanying drawings illustrate my invention somewhat diagrammatically.

Figure 1 is a vert-ical section and Fig. 2 is a horizontal section of an induction furnace made in accordance with my invention.

The metallic crucible 1 makes a single turn about t-he leg of the magnetic core 2, thus actingl as a primary winding with respect to the furnace charge, which acts as a secondary winding. Prima-ry and secondary are insulated from'each other by a refractory insulating lining 4 which bridges` the small gap between the adjacent walls of the crucible at the'regionof connection with the source of current. The operating current is preferably provided by extending the prlmary winding 1 to constitute a secondary winding 5 of one or a few turns of a stepdown transforme-r 6. Thistransformer has a core 7, and. a relatively high potential primary winding 8 as usual. In furnaces of considerable capacity the primary 1 and, in some cases secondary 5, are provided with a duct 9 for the circulation of a cooling fluid such as water.

It will be observed that the current supplied to the furnace is transformed in the step-down transformers 5 to a current of TO GENERAL low voltage and high amperage, the ratio of transformation depending, of course, upon thc supply voltage. This high amperage current is utilized in the furnace by a one vto one transformation to heat the charge 3.

As t-he primary econdary turns are separated only by tliliisiing 4f, there is very little magnetic leakage and the furnace operates with a high power factor.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. In an induction furnace, the combination of a magnetic core, a low resistance Winding on said core adapted to act as a charge-containing furnace chamber, and an insulating lining for said chamber.

2. In an induction furnace, the combinay .tion of a step-down transformer, the low voltage secondary being extended to form a single turn primary for a second transformation and adapted to support a charge to constitute a secondary circuit with respect thereto, and means for insulating Said charge from the primary.

3. In an induction furnace, the combination of a magnetic core, a metallic crucible surrounding the same constituting a primary winding and adapted to Acontain a charge constituting the secondary winding, and means for supplying to said primary winding a variable current of low voltage and high amperage.

4. In an induction furnace, the combinaing a charge constituting a Winding on said said charge from the cruciblei core, and a single turn primary winding of In Witness whereof, I have' hereunto set 10W reslstance located in close inductive remy hand this 25th day'of July, 1911.

tion of a magnetic core, means for supportfurnace charge, and means for insulating 5 lation to said charge. CHARLES P. STEINMETZ.

5,. Inan induction furnace, the combina- Witnesses: tion of asingle turn primary, consisting of BENJAMIN B. HULL,

a metallic Crucible Yadapted to conta-in a HELEN ORFORD. 

